Bose-Einstein Condensation and Supersolids

TL;DR

This paper explores conditions under which Bose-Einstein condensates and supersolids can exist at finite temperatures in different dimensions, highlighting the roles of interaction range and external potentials.

Contribution

It introduces a new understanding of supersolid formation at finite temperatures, including the correct Bloch wave function for such states.

Findings

3D supersolids possible without external potential

2D supersolids require nonlocal, long-range interactions

No BEC or supersolid at finite temperature with lattice potential in 2D

Abstract

We consider interacting Bose particles in an external potential. It is shown that a Bose-Einstein condensate is possible at finite temperatures that describes a supersolid in three dimensions (3D) for a wide range of potentials in the absence of an external potential. However, for 2D, a self-organized supersolid exists for finite temperatures provided the interaction between bosons is nonlocal and of infinitely long-range. It is interesting that in the absence of the latter type of potential and in the presence of a lattice potential, there is no Bose-Einstein condensate and so in such a case, a 2D supersolid is not possible at finite temperatures. We also propose the correct Bloch form of the condensate wave function valid for finite temperatures, which may be used as the correct trial wave function.